Abstract

Background: Direct-acting antivirals (DAA) are highly effective for treating hepatitis C virus (HCV) infection even among people who inject drugs (PWID). Yet, little is known about patients' adherence patterns and association with sustained virologic response (SVR) rates. We aimed to summarize various adherence patterns and determine their associations with SVR.

Methods: Electronic blister packs were used to measure daily adherence to once-a-day sofosbuvir/velpatasvir during the 12-week treatment period among active PWIDs. Blister pack data were available for 496 participants who initiated DAA, and had ascertained SVR status. Adherence was summarized in multiple patterns, such as total adherent days, consecutive missed days, and early discontinuations. Thresholds for adherence patterns associated with >90% SVR rates were also determined.

Results: The overall SVR rate was 92.7% with median 75% adherence rate. All adherence patterns indicating greater adherence were significantly associated with achieving SVR. Participant groups with 42/84 (50%) or more adherent days, or less than 26 consecutive missed days achieved >90% SVR rate. When adherence was stratified by <50% versus ≥50%, only among those with <50% adherence, greater total adherent days during 9-12 weeks, and no early discontinuation were significantly associated with higher SVR rate. Participants with first month discontinuation and ≥2 weeks of treatment interruption had low SVR rates, 25% and 85%, respectively. However, greater adherent days were significantly associated with SVR (aOR = 1.10 (1.04, 1.16), p<.001) even among participant with ≥14 consecutive missed days.

Conclusions: Although suboptimal adherence can still result high SVR rates among PWID population, encouraging patients to take as much medication as possible, with fewer than 2 weeks consecutive missed days, and without early discontinuation, was found to be important for achieving SVR.

Clinical trial number: NCT02824640.